1. Field of the Invention
The present invention relates to methods for placental exfoliation and methods for parturition induction, for example.
2. Background Art
The livestock industry related to farm animals such as cattle is said to be profitable provided with the successful reproduction. However, in the case of Hokkaido Japan, the economic loss caused by the deterioration in the reproductive performance has been preliminarily calculated as 3 million yen or more per dairyman on average. As one of the causative factors of this deterioration in the reproductive performance, technical inadequacies and accidents related to the parturition can be enumerated. These technical inadequacies and accidents related to the parturition lead to the increase in the mortality rate of newborns and the lowering in the success rate of conception. Moreover, overworks involved in the attendance in the midnight parturition are also raising big problems at the production site of the livestock industry where aging of stock raising farmers is in progress.
Under such situations, the parturition-related techniques required by stock raising farmers include techniques for safely inducing the daytime parturition so as to avoid the attendance in the midnight parturition, and parturition induction techniques for preventing the placental retention so as to avoid a difficult delivery caused by an oversized fetus beyond the due date. These techniques bring up various effects such as reduced incidence of accident during the parturition, alleviation of mental and physical strain on the manager, appropriate management of the newborn (supply of colostrum without delay), and normal recovery of a maternal farm animal after parturition.
Examples of the above parturition-related techniques which are conventionally performed include, in cases of cows, the induction of daytime parturition by limiting the feeding time and the parturition induction using hormones (glucocorticoid or prostaglandin).
The induction of daytime parturition by limiting the feeding time is specifically performed by feeding during the night time, removing the leftover in the morning, and giving no food during the day time (Wolfe, Modern veterinary practice, Vol. 64, p. 21-23 (1983); and Aoki et al., Animal Science Journal, Vol. 77, No. 3, p. 290-299 (2006)). However, the concerned induction yields about 70% probability of the daytime parturition. Moreover, it is unknown when the parturition after the treatment occurs. Furthermore, this technique can not be used for cows suffering from prolonged gestation when calving would not occur even after a long-delayed due date.
As shown in FIG. 1, the parturition is achieved in two stages of the fetal delivery and the placental release. In the abovementioned parturition induction using glucocorticoid or prostaglandin, the fetal delivery serving as the first stage of the parturition is induced. Glucocorticoid promotes the production of prostaglandin and prostaglandin has luteolytic and oxytocic actions. Because of these actions, the administration of glucocorticoid or prostaglandin induces the fetal delivery (Nakahara et al., Kachiku Hansyokushi (Journal of Veterinary Reproduction), Vol. 21, No. 4, p. 135-140 (1976); Uemura et al., Kachiku Hansyokushi (Journal of Veterinary Reproduction), Vol. 23, No. 3, p. 85-91 (1977); and Aihara et al., Kachiku Shinryo (Journal of Veterinary Clinic), Vol. 52, No. 11, p. 673-681 (2005)). In the concerned parturition induction, calving occurs within about 1.5 to 2 days post administration of glucocorticoid or prostaglandin, although the incidence of the placental retention is high. Accordingly, the concerned parturition induction has problems such as a pathologic condition in which the placenta is not released even though the fetus is delivered (retained afterbirth).
In this way, there has been no known safe and innovative technique for controlling the parturition yet.